Current sampling circuit suitable for high-frequency switching power supply

Abstract

The utility model relates to the technical field of switching power supply circuits, and provides a current sampling circuit suitable for a high-frequency switching power supply, which comprises a system input end filter capacitor DC0, an inductor L1, a high-frequency filter capacitor C1, a HALL current sensor, an inductor L2, an output filter capacitor DC1 and a secondary LC filter consisting of the inductor L2 and the capacitor DC1. Through the design of the two-stage LC filter, the filtering constant is controlled to be 1 / 3 of the system response frequency, so that the current sampling rate is improved, the ripple noise of the system is reduced, and the stability and the power supply quality of the power supply system are improved. Meanwhile, the design reduces the dependence on a high-speed Hall current sensor, and effectively reduces the cost of the sampling circuit. The current sampling circuit provided by the utility model can adapt to application scenes with higher frequency in a future high-frequency switching power supply, and meets requirements brought by upgrading of semiconductor devices.

Description

Technical Field

[0001] The utility model relates to the technical field of switching power supply circuits, in particular to a current sampling circuit suitable for high-frequency switching power supplies. Background Art

[0002] From the development history of power supply, the 50 Hz industrial frequency power supply has advanced to the 400 Hz medium frequency power supply. With the birth of transistor materials, a high-frequency switching power supply based on kilohertz frequency has been developed. Compared with industrial frequency power supply and medium frequency power supply, the switching power supply has the characteristics of small size and light weight. With the continuous exploration of semiconductor devices by humans, the third-generation semiconductor technology of silicon carbide and gallium nitride has gradually entered the field of vision of the application layer. However, with the continuous increase in frequency, the adaptability of various parts in the power supply system to high frequency needs to be further improved, especially the current sampling circuit is more important.

[0003] Taking digital power supply as an example, in order to adapt to the characteristics of gallium nitride transistors, it needs to be adjusted at a switching frequency of 300kHz. Generally, the maximum adjustment sampling period of digital power supply is 30kHz, which means that the PWM pulse width will be adjusted once in 10 switching cycles. However, the PID adjustment response of the system has hysteresis. If the operation is not done properly, overcurrent may occur at any time. At this time, the necessity of current sampling rate is reflected.

[0004] Due to the continuous updating of semiconductor devices, the required switching frequency is getting higher and higher, resulting in an increase in the system response frequency. At the same time, the required current sampling speed must also be faster, so the sampling process must rely on high-speed Hall current sensors. High-speed Hall current sensors are expensive, making the cost of the sampling circuit high. Utility Model Content

[0005] In order to solve the problems existing in the background technology, the utility model provides a current sampling circuit suitable for a high-frequency switching power supply, comprising:

[0006] The system input filter capacitor DC0 has a positive end connected to the input terminal VIN+ and the D pole of the transistor Q1, and a negative end connected to the input terminal VIN-, the S pole of the transistor Q2, the 2 ends of the high-frequency filter capacitor C1, and the negative end of the output filter capacitor DC1;

[0007] An inductor L1, one end of which is connected to the S pole of the transistor Q1 and the D pole of Q2;

[0008] High frequency filter capacitor C1, one end of which is connected to the other end of the inductor L1 and the input end of the HALL current sensor;

[0009] The output end of the HALL current sensor is connected to the terminal 1 of the inductor L2;

[0010] Inductor L2, two ends of which are connected to the positive end of the output filter capacitor DC1;

[0011] Output filter capacitor DC1, its positive end is connected to the 2nd terminal of inductor L2, and its negative end is connected to load LOADA;

[0012] Inductor L2 and capacitor DC1 form a two-stage LC filter.

[0013] Inductor L2 and capacitor DC1 form a two-stage LC filter, whose filtering constant is controlled at 1 / 3 of the system response frequency.

[0014] In a preferred solution, the filtering constant of the two-stage LC filter composed of the inductor L2 and the capacitor DC1 is controlled at 1 / 3 of the system response frequency.

[0015] The beneficial effects achieved by the utility model are:

[0016] The current sampling circuit of the utility model is designed with a two-stage LC filter, which improves the current sampling rate, responds to system changes more quickly, and reduces the risk of overcurrent caused by the hysteresis of the PID regulation response. The use of the two-stage LC filter effectively reduces the system ripple noise caused by high-frequency switching operations, and improves the stability and power supply quality of the power supply system. By reasonably controlling the filter constant, the dependence on high-speed Hall current sensors can be reduced, and the cost of the sampling circuit can be reduced. The current sampling circuit of the utility model can adapt to higher-frequency application scenarios in future high-frequency switching power supplies, and meet the switching frequency requirements that increase with the upgrading of semiconductor devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is the overall circuit diagram of the utility model;

[0018] Figure 2 This is a circuit diagram of a traditional Hall current sensor for current sampling. DETAILED DESCRIPTION

[0019] The technical solution of the utility model will be clearly and completely described below in conjunction with the drawings in the utility model. In addition, the forms of the various structures recorded in the following embodiments are merely illustrative, and the utility model is not limited to the various structures recorded in the following embodiments. All other implementations obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the utility model.

[0020] The traditional Hall current sampling circuit is as follows Figure 2As shown in the figure, due to the update of semiconductor devices, the switching frequency is getting higher and higher. As the switching frequency is getting higher, the system response frequency must also be higher. At the same time, the required current sampling speed must also be faster, so expensive high-speed Hall current sensors must be used. Figure 1 , a current sampling circuit suitable for high-frequency switching power supply, including a system input filter capacitor DC0, whose positive end is connected to the input terminal VIN+ and the D pole of the transistor Q1, and whose negative end is connected to the input terminal VIN-, the S pole of the transistor Q2, the 2 ends of the high-frequency filter capacitor C1 and the negative end of the output filter capacitor DC1; an inductor L1, whose 1 end is connected to the S pole of the transistor Q1 and the D pole of Q2; a high-frequency filter capacitor C1, whose 1 end is connected to the 2 ends of the inductor L1 and the input end of the HALL current sensor; the HALL current sensor, whose output end is connected to the 1 end of the inductor L2; an inductor L2, whose 2 ends are connected to the positive end of the output filter capacitor DC1; an output filter capacitor DC1, whose positive end is connected to the 2 ends of the inductor L2, and whose negative end is connected to the load LOADA; the inductor L2 and the capacitor DC1 form a secondary LC filter. The inductor L2 and the capacitor DC1 form a secondary LC filter, and its filtering constant is controlled at 1 / 3 of the system response frequency. The filtering constant of the two-stage LC filter composed of inductor L2 and capacitor DC1 is controlled at 1 / 3 of the system response frequency.

[0021] The system design configuration of the utility model is as follows:

[0022] Change the control algorithm of the power system to an average current algorithm to reduce the response requirements of the current sensor for high-frequency sampling. Using a general current sampling Hall sensor can meet the requirements: Add a secondary LC filter and calculate the secondary filter LC filter constant Match this constant with the system response frequency and control it at 1 / 3 of the system response frequency.

[0023] Embodiment 1:

[0024] In this embodiment, the response frequency of the design system is 30kHz, and the filter constant formed by them can be controlled to be around 10kHz by adjusting the inductance "L" of L2 and the capacitance "C" of DC1. If the inductance of inductor L2 is configured to be 1uH and the capacitance of capacitor DC1 is configured to be 220uF, the LC filter constant formed by them is calculated as follows:

[0025]

[0026] The filtering constant meets the system matching requirements, and this configuration can suppress the peak current ripple within the response range of the general current sampling Hall.

[0027] This circuit adds a second level filter, and the reasonable configuration of the filter constant can reduce the system's requirements for the current sampling rate, so ordinary current sensors can be used. The current sampling interface is introduced into the hardware comparator interface, which can be used as an interrupt protection when necessary.

[0028] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A current sampling circuit suitable for a high-frequency switching power supply, characterized in that: include: The system input filter capacitor DC0 has a positive end connected to the input terminal VIN+ and the D pole of the transistor Q1, and a negative end connected to the input terminal VIN-, the S pole of the transistor Q2, the 2 ends of the high-frequency filter capacitor C1, and the negative end of the output filter capacitor DC1; An inductor L1, one end of which is connected to the S pole of the transistor Q1 and the D pole of Q2; High frequency filter capacitor C1, one end of which is connected to the other end of the inductor L1 and the input end of the HALL current sensor; The output end of the HALL current sensor is connected to the terminal 1 of the inductor L2; Inductor L2, two ends of which are connected to the positive end of the output filter capacitor DC1; Output filter capacitor DC1, its positive end is connected to the 2nd terminal of inductor L2, and its negative end is connected to load LOADA; Inductor L2 and capacitor DC1 form a two-stage LC filter; Inductor L2 and capacitor DC1 form a two-stage LC filter, whose filtering constant is controlled at 1 / 3 of the system response frequency.

2. The current sampling circuit suitable for high-frequency switching power supply according to claim 1, characterized in that: The filtering constant of the two-stage LC filter composed of inductor L2 and capacitor DC1 is controlled at 1 / 3 of the system response frequency.

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